This invention relates to a form of a pipette known as a pipette pump and, more particularly, to an improvement in pipette pumps to facilitate discharge of the contents of a pipette.
There are, broadly speaking, two principal forms of pipetting. In the first form, the pipette is filled with a desired quantity of liquid and subsequently, the entire contents of the pipette are emptied either rapidly or more gradually. Regardless of whether the contents of the pipette are emptied gradually or rapidly, pipettes of this first type are quite accurate and used for precise quantitative measurements.
A second form of pipetting, frequently referred to as serological pipetting, is semi-quantitative in that a pipette is filled with a quantity of liquid and thereafter the liquid is discharged into a plurality of aliquots. This may be thought of as sequential transfer or discharge of the contents of the pipette.
The pipette equipment, which is to some extent usable either for accurate pipetting or for semi-quantitative, sequential discharge pipetting, has heretofore been of essentially two different types. In a first type of equipment, a hollow tube, or pipette, made of glass or plastic and open at both ends, has one end lowered into a fluid to be transferred until the fluid reaches a desired level within the pipette. Then, the laboratory technician covers the opposite, or open end, of the pipette, such as with a thumb or forefinger, the pipette with some liquid therein is removed, and the pipette moved to a second location. The laboratory technician then releases the top of the pipette, and the entire contents of the pipette are discharged. This type of pipette works solely by virtue of atmospheric pressure and gravitational forces. It may be appreciated that by selectively covering and releasing the top of the pipette tube, the technician may achieve a quasi-quantitative approach to sequentially discharging the contents of the pipette at a plurality of locations.
A second type of pipette, frequently called a pipette pump, includes a form of mechanical device, e.g., valves, bellows, pump, piston, plunger, wheel, etc. The pipette is placed within the fluid to be transferred, and the mechanical device is actuated to fill the pipette. Then the pipette is moved to the location where the contents are to be discharged, and the mechanical device, or pump, is actuated. Competitive products presently available usually provide alternate forms of dispensing, a rapid dispensing and a more gradual dispensing. This second type of pipette is frequently identified as a positive displacement or piston displacement pipette. Examples of prior pipettes of the type heretofore described are illustrated at page 101 of the PGC Scientifics Catalog. It may be appreciated that with mechanical pipette pumps, the prior art devices have heretofore provided either two alternate mechanical devices (e.g., wheel and plunger, wheel and lever) or a plurality of valves.
Pipettes which do not employ a pump mechanism are, of course, more easily emptied, but potential problems arise in the handling of corrosives and biological fluids such as blood, urine and the like. For example, because of the potential for spread of hepatitis and/or HIV virus, laboratory technicians, even though wearing latex protective gloves, frequently object to utilizing such pipettes.
Thus, prior to the present invention, there have been no satisfactory solutions to obtaining the benefits of a semi-quantitative pipette, of the type typically used with serological studies where the contents are discharged or dispensed into a plurality of aliquots, which are easy and convenient to use and which minimize the risk of exposure of the laboratory technician to the biological fluid.